1. Field of the Invention
The present invention relates to an electric power steering system and a method of processing a fail-safe of an electronic control unit.
2. Description of the Prior Art
With the rapid advancement of automotive technology, technical development for various apparatuses for convenience is consistently made for the convenience of drivers.
Among them, an electric power steering system provides a steering assist force by driving an electric motor when a driver operates a steering wheel of a vehicle so as to reduce the driver's steering burden.
In order to control the electric motor, the Electronic Control Unit (ECU) of the electric power steering system should receive a steering torque signal—a signal generated by measuring the steering torque generated by the user to operate the steering wheel—from a torque sensor.
The torque sensor refers to a device configured to convert the steering torque of the steering wheel generated by the driver's steering intention into an electric signal. The torque sensor is installed to the electric power steering system so as to measure the torque of the steering wheel.
In the existing electric power steering system, one fail-safe method for a failure of the torque sensor is to stop the operation of the electric power steering system when the failure of the torque sensor occurs, and then switch the steering system into a manual mode, for example.
However, when the electric power steering system is switched to the manual mode due to the failure of the torque sensor, the steering assist force is momentarily lost, which causes deterioration in stability in the driver's steering.
In particular, in the case of low speed traveling, there is a problem in that the steering force to be burden to the driver sharply increases as the steering assist force is lost.